Anticorrosive lubricating oil composition



Patented Feb. 27, 1951 ANTICORROSIVE LUBRICATING OIL COIVIPOSITION Raymond W. Mattson, Long Beach, Calif., as-

signor to Union Oil Company of California, L08 Angeles, Calif., a corporation of California No Drawing.

Application May 27, 1946,

Serial No. 672,723

This invention relates to an improved lubricating oil composition and to the method for preparing the same. In particular the invention relates to lubricating oil, particularly a mineral lubricating oil containing certain derivatives of the condensation products of mercaptans and organic carbonyl compounds as will be hereinafter specified and to lubricating oils containing such additives together with other addition agents, such as detergents and/or anticorrosion agents.

It is well known to those familiar with the art that conventionally refined lubricating oils subjected to the heavy duty service required by internal combustion engines in trucks, busses, tractors, tanks, etc., suffer serious and rapid oxidation and deterioration which results in impaired operation of, or damage to, the engine. One of the efiects of this oil deterioration is corrosion of bearings, especially bearings of the hard alloy type, such as copper-lead or cadmium-silver bearings. Another serious disadvantage attendant to the use of conventionally refined lubricating oils in heavy duty service is the deposition of sludge, lacquer, varnish, and other oil-insoluble carbonaceous materials on the various parts of the engine. This often results in piston ring sticking with consequent decrease in engine efiiciency because of blow-by and loss of compression. Plugging of oil ring slots and ring groove oil holes also occur with resulting increased engine wear and oil consumption. Other deposits in oil lines may retard or prevent the flow of oil to moving parts so that failure may result from lack of lubrication.

The principal object of this invention is to provide a lubricating .oil which is resistant to oxidation and deterioration in heavy duty service, which will be non-corrosive to alloy type bearings, which will prevent the formation and deposition of varnish, lacquer, sludge and other insoluble carbonaceous materials in piston ring grooves, oil holes, and other parts of the engine, and which will prevent the sticking of piston rings.

To overcome the above disadvantages of a mineral lubricating oil in heavy duty service, many additives have been proposed in the past. In general these additives are of two types, detergents and bearing corrosion inhibitors which are generally referred to as anticorrosion agents. A detergent is added to the oil to retard or prevent lacquering and fouling of the engine. The anti- 13 Claims. (Cl. 252-465) ing in detergency.

corrosion agent is added to reduce corrosion of the bearings and other corrosion sensitive parts of the engine. Although both anticorrosion and detergent properties are sometimes claimed for a single additive, the general practice is to employ combinations of two or more additives each of which contributes a desired property to the oil so that the final blend will be satisfactory for the use for which it is intended.

Moran et al. in United States Patent No. 2,322,093, have disclosed the use of certain mercaptals, mercaptols and trithio ortho esters in highly refined mineral oils, such as transformer oils, parafiin wax and the like, for the purpose of inhibiting oxidation of the oil. I have found that these compounds when employed alone are unsatisfactory lubricating oil additives for use in solvent refined lubricating oils under heavy duty service. Oils containing the simple mercaptals, mercaptols, or trithio ortho esters are unsatisfactory because generally such oils exhibit excessive bearing corrosion and more particularly these oils are substantially always lack- However, by following the practices of this invention, as will now be more fully described, an improved lubricating oil composition is obtained which has all of the desirable characteristics mentioned hereinabove.

The above and other objects, which will be apparent hereinafter, have been attained by providing a lubricating oil, particularly a mineral lubricating oil, having dissolved therein a minor proportion of the reaction product between a mercaptan and a compound containing at least one group. Such products will be referred to hereinafter as condensation products. The compounds containing at least one group include aldehydes, ketones, acids, esters, aldehyde acids, diketones, keto acids, and the like. It is also an important feature of the invention that these compounds contain at least one -OR group, where R is a radical selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl and alkaryl radicals. The condensation reaction is carried out 3 under conditions such that water is eliminated with the formation of a compound of the formula where X=C represents an aldehyde or ketone residue; Y-C represents a carboxylic acid residue resulting from the reaction of either an acid or an ester with the mercaptan; R represents a radical of the group consisting of alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl. aralkyl and alkaryl radicals. The radical R, which is the mercaptan residue, may be a simple hydrocarbon radical, that is, one of the types indicated or itmay be a substituted hydrocarbon radical. Thus the radical may be substituted with one or more groups, such as R (where R is substantially any hydrocarbon radical or hydrogen), N02, SOaH, C1. and Br like groups.

The presence of at least one OR group in the aldehyde, ketone, acid or ester residue of the resulting mercaptal, mercaptol or trithio ortho ester appears to improve the value of the condensation product as a lubricating oil additive inasmuch as additives of this type have been found to be superior in regard to either detergency or anticorrosive effect and particularly the latter, to the mercaptals, mercaptols or trithio ortho esters which do not contain this -OR group, regardless of what other substituents may be prescut.

The condensation of a carbonyl compound with a mercaptan results in the formation of three types of compounds depending upon the type of carbonyl compound employed. 'lhe condensation product of an aldehyde with a mercaptan is called a mercaptal, ketones yield mercaptols and acids or esters yield trithio ortho esters. Condensation is usually eflfected using a solution or mixture of the carbonyl compound and mercaptan in the presence of gaseous hydrogen chloride. Methods for carrying out the condensation reaction are well known in the art and are described by Posner, Berichte, volume 33, page 2987 (1900).

Condensation of the carbonyl compound and the mercaptan is effected most conveniently in the following manner. A mixture or solution of stoichiometrically equivalent quantities of the carbonyl compound and the mercaptan, which correspond to 1 mole of aldehyde, ketone and/or ester to 2 moles of mercaptan, is heated to 120 F. to 140 F. At that temperature gaseous HCl is bubbled into the reaction mixture with stirring. Considerable heat is given oil? by the reaction so that cooling is necessary during the first few minutes to maintain the temperature in the desired range. Thereafter a slight amount of added heat may be required. The stream of HCl gas is continued with stirring at the above temperature for about two hours. The reaction mixture is then allowed to cool to room temperature and to stand for 12 to 16 hours. after dilution with a volatile solvent, such as benzene, the solution is washed several times with water to remove HCl, dried over Na2SO4, and topped to yield the finished product. It is preferable to use reduced pressure-during the final topping so that all solvent and traces of unreacted material may be removed at temperatures not over about 212 F. to 257 F.

The aldehydes, ketones, acids and esters which may be used to prepare the condensation products of this invention may contain from 2 to 18 or more carbon atoms per molecule. Moreover, these compounds may be an aliphatic, unsaturated, aromatic, cyclic, or alkylated aromatic compound. Carbonyl compound conta.ning at least one -OR group which may be used include diacetone alcohol, salicylaldehyde, 2-hydroxy-3-methoxy benzaldehyde and 4-hydroxy-3-methoxy benzaldehyde, m-hydroxybenz:.ldehyde, p-hydroxybenzaldehyde, the 2,3-, 2,4-, 2,5-, 2,6-, and 3,4-di hydroxybenzaldehyde, resacetophenone, methoxyacetic acid, the ortho and paramethoxybenzaldehydes, p-methoxybenzophenone, p-methoxybenzoic acid, methylanisate, lactic acid, citric acid, methyl citrate, ethyl lactate, and like compounds.

Mercaptans which may be used to react with the carbonyl compounds may contain from 1 to 18 or more carbon atoms. The mercaptan may be saturated or unsaturated, aromatic or cyclic, paraflinic or isoparaflinic, substituted or unsubstituted. Particularly suitable mercaptans ininclude ethyl mercaptan, normaland isopropyl mercaptans, normaland isobutyl mercaptans, normal-octyl mercaptan, and benzyl mercaptan.

The resulting condensation product should be sufliciently oil-soluble or oil dispersible that it may be used inthe concentrations later specified. Oil-solubility is a function of the size and number of hydrocarbon radicals in the molecule, particularly in relation to the number of OR or other polar groups which may be present, which polar groups have the effect of decreasing oil-solubility. Thus oil-solubility may be increased by increasing the hydrocarbon portion, particularly the alkyl hydrocarbon portion of either the carbonyl compound or the mercaptan, or both. For example, the diisobutyl mercaptal of 2-hydroxy-S-methoxy benzaldehyde is soluble in a viscosity index solvent refined mineral lubricating oil to the extent of about 1% by weight. The di-normal-octyl mercaptal of 2-hydroxy-3- methoxy benzaldehyde, on the other hand, is freely soluble in the same oil.

Although the above described mercaptals, mercaptols and trithio ortho esters containing at least one OR group are lubricating oil addition agents of particular merit I have found that these compounds may be increased in their effectiveness, particularly in regard to their detergency, by converting them into phosphorus and sulfur-containing compounds. Thus I have found that by reacting these condensation produets with a sulfide of phosphorus, in the ratio of between about 5 and about 7 parts by weight of condensation product per part of phophorus compound, and then neutralizing the resulting product with a metal base, there is produced an improved lubricating oil addition agent.

It is therefore a feature of the invention that the above mentioned condensation products, i. e., the mercaptals, mercaptols and trithio ortho esters containing at least one OR group may be reacted with a sulfide of phosphorus, such as P255, P233, and P483, to form an acidic product and the acidic product then neutralized with a metal base to form an oil-soluble metal salt. These reaction products will be referred to as oil-soluble metal salts of phosphosulfurized condensation products of a mercaptan and a carbonyl compound. The metal base is preferably an alkaline earth metal oxide or hydroxide, as for example an oxide or hydroxide of calcium, barium, strontium or magnesium, although many polyvalent metal bases produce desirable metal salts. Thus, zinc, lead, tin, aluminum, manganese, nickel, cobalt and like polyvalent metal salts of the phosphosulfurized condensation products are all valuable lubricating oil addition agents. If desired the sodium or other alkali metal salt may be prepared and the product then converted into a polyvalent metal salt by metathesis with a polyvalent metal salt.

The above described salts may be prepared by the direct reaction of phorphorus pentasulfide, the preferred phosphorus compound, with the mercaptal, mercaptol or trithio ortho ester at a temperature between about 122 F. and 302 F., and preferably between about 158 F. and 212 F. If desired, the heating may be carried out in the presence of a hydrocarbon solvent refluxing in the appropriate temperature range. This has been found to be a particularly effective means for controlling the temperature during the reaction, which, it should be pointed out, is exothermic. A reaction time of 6 to 8 hours is generally sufficient to insure completion of the reaction. The reaction product is filtered and neutralized with a metal base to form the oil-soluble metal salt. Neutralization is efiected by refluxing the above reaction product with an excess of a metal oxide or hydroxide. Also, the salts may be prepared by refluxing the acidic reaction product with a base, such as calcium hydroxide, in the presence of a solvent for about two hours, and then filtering and topping the refluxed product to yield the oil-soluble metal salt.

Mercaptals, mercaptols or trithio ortho esters other than those containing an -OR group may be employed to react with P235 to produce valuable lubricating oil addition agents. Thus condensation products which contain olefinic groups within the molecule or other hydrocarbon groupings which are reactive toward P255 have been found to yield phosphorus and sulfur-containing salts having desirable detergent and anticorrosion properties. Mercaptals or mercaptols which furnish such groupings may be exemplified by the condensation product of a, mercaptan with isophorone which may then be reacted with P255 and neutralized as described above.

Although I may employ the condensation products or the salts of the phosphosulfurized condensation products as the only additive in the preparation of the high quality lubricating oils of my invention I may use either one or both of these additives together with other lubricating oil additives, such as detergents and/or anticorrosion agents, I find that if a detergent, such as an oilsoluble metal sulfonate, is used in conjunction with either the condensation product or the salt of the phosphosulfurized condensation product the resulting oil has excellent detergency as well as anticorrosion characteristics.

Detergents which are particularly valuable for use in conjunction with one or both of the above described additives include in addition to the mentioned oil-soluble metal salts of sulfonic acids and particularly petroleum sulfonic acid salts the oil-soluble metal salts of fatty acids, halogenated fatty acids or substituted fatty acids, such as dichlorostearic acid and phenylstearic acid; oilsoluble metal salts of rosin acids or hydrogenated rosin acids, such as abietic acid or hydrogenated abietic acid; oil-soluble metal salts of acids produced by the oxidation of high molecular weight paraflinic hydrocarbons or hydrocarbon fractions, such as parafiin wax, highly paraifinic lubricating oil fractions, and the like.

Anticorrosion agents which may be employed in conjunction with any or all of the above described additives include oil-soluble metal salts of phenols, particularly alkyl substituted phenols having more than about 12 carbon atoms per molecule; oil-soluble metal salts of phenol sulfides or alkyl or cycloalkyl substituted phenol sulfides and particularly those having alkyl substituents containingat least about 4 carbon atoms; oil-soluble metal salts of the reaction products formed by reacting a sulfide or oxide of phosphorus with an alcohol or phenol; oil-soluble metal salts of phosphonic or phosphinic acids obtained by reacting elemental phosphorus with hydrocarbons.

The oil-sol-uble metal detergent and anticorrosion salts are preferably polyvalent metal salts,

the alkaline earth metal salts being particularly preferred. However, any of the metals described 'as forming desirable metal salts of the phosphosulfurized condensation products may be employed in preparing desirable detergents and anti corrosion agents.

In preparing the high quality lubricating oils of this invention the desired quantity of addition agents or agents is dissolved in the lubricatingoil. In general the additives are sufiiciently oil-soluble that ordinary simple blending operations, such as stirring (with or without the use of heat depending upon the viscosity of the oil employed) are sufficient to obtain complete solution or dispersion of the additives in the oil. Substantially any type of lubricating oil may be employed although an oil of high quality is preferred. Thus Eastern mineral lubricating oils such as those generally known as Pennsylvania oils and particularly solvent refined Western mineral lubricating oils of about V..I. are the preferred base oils.

The amounts of additives to be employed will depend upon the type and quality of mineral oil employed as well as upon the type of service in which the finished oil is to be employed. .In general the mercaptals and mercaptols and trithio ortho esters or the oil-soluble salts of the phosphosulfurized mercaptals, mercaptols and trithio ortho esters may be employed in amounts ranging from about 0.1% to about 3.0% by weight of the finished product and preferably in the range of about 0.5% to 2.0%. These same percentage ranges will apply whether these additives are employed alone or in conjunction with other addition agents, such as detergents and/or anticorrosion agents. The amounts of detergents and of anticorrosion agents which may be employed together with simple condensation products or the salts of phosphosullurized condensation products will generally be in the range of about 0.1% to about 3.0% of the finished lubricant and preferably in the range of about 0.5% to about 2.5% by weight. Typical compositions may contain 1.0% by weight of a mercaptal, for example, and 0.7% by weight of an oil-soluble sulfonate or 1.0% by weight of a mercaptal,.0.7% by weight of an oil-soluble sulfonate and 0.7% by weight of an oil-soluble metal salt of a phenol sulfide.

The following examples are presented to illustrate further the principles of my invention, but it is to be understood that the invention is not to be limited to the methods and materials here presented.

EXAMPLE I Mercaptal containing no -OR groups A solution of grams of bcnzaldehyde in grams of isobutyl mercaptan was saturated with hydrogen chloride gas by bubbling HCl through the solution, with stirring, for hours. Considerable heat was generated initially so that cooling with a water bath was required to maintain a reaction temperature between 122 F. and 140 F. Gentle heating was applied thereafter as required to maintain this temperature. The reaction mixture was then poured into about 500 ml. of water and diluted with about 500 ml. of a parafiinic petroleum naphtha having a boiling range of about 140 F. to 212 F. The water layer was removed and the organic layer washed twice more with 500 ml. portions of water. The organic layer was then dried over anhydrous sodium sulfate, filtered, and the solvent and unreacted materials distilled off, finally at a pressure of 2 mm. with a distillation bottoms temperature of 235 F. The distillation bottoms, amounting to 213 grams, and consisting of diisobutyl benzaldehyde mercaptal was found to contain 23.2% sulfur. This product was dissolved in mineral lubricating oil in the ratio of 1 part of the mercaptal to 99 parts of the oil and the resulting lubricant was tested in a Lauson engine. suits are shown in Table I. Oil No. 2.

EXAMPLEII A mixture of grams of vanillin (2-methoxy- 4-hydroxy-benaldehyde) and 96 grams of normal octyl mercaptan was warmed to 122 F. to eifect partial solution of the vanillin in the mercaptan. Hydrogen chloride gas was passed into the mixture while stirring and cooling or heating as necessary to maintain the temperature at between about 122 F. and 140 F. for one hour, and while cooling to room temperature during an additional half hour period. The mixture was allowed to stand for 16 hours, then diluted with about 500 ml. of benzene and washed five times with about 250 ml. portions of water. The benzene solution was dried over anhydrous sodium sulfate, then the benzene was topped off at about 50 mm. pressure. Finally the residue was subjected to a pressure of 0.6 mm. and a temperature of 223 F. to remove the last traces of benzene and unreacted materials. The product amounted to 133 grams of di-normal-octyl vanillin mercaptal containing 15.25% by weight of sulfur. This product was freely soluble in a 90 V. I. solvent refined parafiin base lubricating oil and oil containing this material was engine tested with the results shown in Tables I and II, Oils Nos. 3, 4, and 7. Oils 4 and 7 contain calcium petroleum sulfonate in addition to the mercaptal.

EXAMPLE III Hydrogen chloride gas was bubbled through a mixture of grams of diacetone alcohol and 106 grams of isobutyl mercaptan contained in a flask surrounded by an ice bath. Treatment with the HCl gas was continued under these conditions for 1% hours and for another 2 hours and 50 minutes at room temperature. The reaction mixture was diluted with a light parafiinic naphtha and washed five times with about 250 ml. portions of distilled water. After drying and topping oil the naphtha, grams of diisobutyi diacetonealcohol mercaptol was distilled from the product at a still head temperature between about 178 F. and 189 F. under a pressure of 2 mm.

A 59 gram portion of this mercaptol and 8.4 grams of pulverized P2Ss were placed in a flask and heated gently for 3 hours, at increasing tem- The engine test reperature, to a final temperature of 221 F. The mixture was diluted with light naphtha, excess lime was added, and the mixture refluxed for 1 hour. The product was filtered and the filtrate was evaporated on a steam bath. The residue was subjected to a temperature of 212 F. at a pressure of 2 mm. of mercury. There remained as product, 30 grams of a red liquid which contained 1.13% phosphorus, 22.91% sulfur, and 0.42% calcium. The product'was freely soluble in lubricating oils and an oil containing 0.8% by weight of this material was engine tested with the results shown in Table 1, 011 No. 5.

EXAMPLE IV Hydrogen chloride gas was bubbled through a mixture of 200 grams of isophorone and 261 grams of isobutyl mercaptan, with stirring, for 6% hours. The temperature rose rapidly and remained between 122 F. and 131 F. for the first hour, after which the mixture gradually cooled down to room temperature. The reaction mixture was diluted with light naphtha and washed several times with water. After drying over anhydrous sodium sulfate, the solution was evaporated on a steam bath and finally subjected to a temperature of 212 F. at 2 mm. pressure, leaving 255 grams of the mercaptan-isophorone reaction product as a residue.

A 250 gram portion of this reaction product, 250 ml. of cleaners naphtha and 50 grams of powdered P235 were placed in a flask and refluxed gently, with stirring, for 5 hours. At this time 100 grams of lime and a few ml. of water were added and the mixture refluxed for 3 hours. The product was filtered and the filtrate was evaporated with stirring while blowing with fuel gas, to a temperature of 356 F. -A 273 gram portion of limed phosphosulfurized isobutyl mercaptanisophorone reaction product was obtained. This product contained 2.46% calcium, 17.8% sulfur, and 3.33% phosphorus. It was readily soluble in a V. I. solvent refined paraflln base lubricating oil and oil solutions containing this product and small amounts of calcium petroleum sulfonate were engine tested with the results shown in Tables I, II, and III, Oils Nos. 6 and 8.

Various engine tests have been used to evaluate the lubricating compositions of my invention and to compare them with oils which do not contain additives and with an oil containing a mercaptal having no --OR groups in the molecule.

Three different engine tests have been used, each test employing a different engine. These engines are the Lauson single cyiinderengine,

I the standard 6 cylinder Chevrolet engine, and a single cylinder Caterpillar Diesel standard test engine. The tests are referred to as the Lauson engine test, the Chevrolet engine test, and the Caterpillar Diesel test, respectively.

In the Lauson engine test, the engine is operated for a total of 60 hours under a load of about 3.5 horsepower with coolant temperature of about 280 F. This test determines the lacquering and corrosion tendencies of the oil. The lacquering tendency of the oil is indicated by a numerical detergency rating determined at the end of the test. The detergency rating is obtained by inspecting the engine at the end of the test and rating it for cleanliness on a scale from 0 to where 100% indicates a clean engine substantially free from sludge, varnish, or lacquer deposits. The corrosivity of the oil is evaluated by determining the loss in weight of the corrosion sensitive copper-lead connecting rod bearing at the end of 20, 40, and 60 hours of operation. In those cases in which the bearing weight loss at the end of 20 or 40 hours of operation was so great as to endanger the engine, a, Babbitt beara coolant temperature of about 200 R and an lo oil temperature of about 280 F. In this test the corrosivity of the oil is indicated by the loss in weight suifered by copper-lead bearings after 8, 16, 24, 36, 44, and52 hours of operation.

The Caterpillar Diesel test measures the detergent qualities of an oil, 1. e., the ability of the oil to prevent deposition of sludge, varnish, and lacquer on the various parts of the engine. In this test the engine is operated for 100 hours under a load of about 19.8 horsepower with a coolant temperature of about 175 F. and an oil temperature of about 145 F. At the end of the test the engine is inspected for cleanliness and a "detergency rating is determined. The detergency rating is based on a scale from 0% to 100% where 100% indicates a substantially clean engine.

The mineral lubricating oil used in the engine tests presented in the following tables was a solvent refined Western lubricating oil of S. A. E.

grade having a gravity of 29.1 A. P. I., a vis- 30 cosity of 540 S. S. U. at 100 F., a viscosity gravity constant of 0.806, and a viscosity index of 90.

TABLE III Caterpillar Diesel tests Detergency 3 Composition Rating,

' Per Cent 1 Mincratl lubricating oil without addition agen s. 8 96.54% oil (Oil No.1), 1.04% limed phosphosul- 77% furized istbutyl mcrcaptan-isophorone rcaciion product from Example IV, 2.4% Ca petroleum sullonate.

The foregoing description is not to be taken as limiting my invention but only as illustrative as many variations may be made by those skilled in the art without departing from the spirit or the scope of the following claims.

I claim:

1. A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% by weight suflicient to impart anticorrosion properties to said oil of a compound of the class consisting of mercaptals, mercaptols and trithio ortho esters, said compound containing at least one substituent OR group where R represents a radical of the class consisting of hydrogen and hydrocarbon radicals.

2 A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% by weight sufficient to impart anticorrosion properties to said oil of an oil-soluble metal salt of the product obtained by treating between about 5 TABLE I Lauson engine tests t'ilit Detergency e g 3 Composition Rating, MKS Hours Per Cent 1 Mineratl3 lubricating oil without addition 58 200 000 ngen 2 90% oil (Oil No. l), 1% diisobutyl benzaldc- 32 44 146 261 hyde mercnptel from Example I. 3.-..-- 98.3% oil (Oil No. 1), 1.7% di-n-octyl vnnillin 22 4 4 G mcrcaptal from Example II. 4 05.75% oil (Oil No. l), 1.7% di-n-octyl vanillln 73 0 8 9 mercaptal from Example II, 1.5% calcium petroleum sulronate. 5 90.2% oil (Oil No. 1). 0.8% limed phosphosul- 38 0 26 163 iurized diisobutyl diacctone. alcohol morcaptel from Example III. 6 96.45% oil (Oil No. l), 1.15% limed phospho- 1'2 5 20 49 suliurized isobutyl mcrcaptan-isophorone reaction product from Example IV, 2.1% Ca petroleum sullonate.

l Cu-Pb bearing replaced by Babbitt hearing at 40 hours due to excessive corrosion.

and about 7 parts by weight of a compound of the class consisting of mercaptals, mercaptols and trithio esters with one part by weight of a phosphorus sulfide at a' temperature between 122 F. and 302 F.

3. A lubricating oil according to claim 2 in which said phosphorus compound is phosphorus pentasulfide.

4. A lubricating composition according to claim 2 in which said oil-soluble metal salt is a calcium salt.

5. A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% by weight suflicient to impart anti-corrosion properties to said oil, of an oil-soluble metal salt 01' the product obtained by treating between about 5 and about 7 parts by weight 01' a compound of the class consisting of mercaptals, mercaptols and trithio ortho esters, said compound containing in which said oil-soluble metal salt is an alka-' line earth metal salt.

8. A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% each of an oil-soluble metal suli'onate and a compound of the class consisting of mercaptals, mercaptols and trithio ortho esters, said compound containing at least one substituent -OR group where R represents a radical of the class consisting of hydrogen and hydrocarbon radicals.

9. A lubricating composition according to claim 8 in which said oil-soluble metal sulfonate is a calcium petroleum sulfonate.

10. A lubricating composition comprising mineral lubricating oil containing 0.5% to 2.5% by weight of an oil-soluble metal sulfonate and 0.5% to 2.0% by weight of a compound of the class consisting of mercaptals, mercaptols and trithio ortho esters, said compound having at least one substituent OR group where R represents a radical of the class consisting oi. hydrogen and hydrocarbon radicals.

11. A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% by weight each of an oil-soluble metal sultonate and an oil-soluble polyvalent metal salt of the product obtained by treating between about 5 and 12 about 7 parts by weight 01' a compound of the class consisting of mercaptals, mercaptols and trithio ortho esters with one part by weight 01' a phosphorus sulfide at a temperature between 122 F. and 302 F.

12. A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% by weight, suilicient to impart anticorrosion properties to said oil, of a mercaptal containing at least one substituent OR group where R represents a radical of the class consisting of hydrogen and hydrocarbon radicals.

13. A lubricating composition comprising mineral lubricating oil containing 0.1% to 3.0% by weight, suflicient to impart anticorrosion properties to said oil, of a mercaptol containing at least one substituent -'-OR group where R represents a radical of the class consisting oi hydrogen and hydrocarbon radicals.

RAYMOND W. MA'I'I'SON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,242,260 Prutton May 20, 1941 2,257,751 Lincoln Oct. 7, 1941 2,289,795 McNab July 14, 1942 2,308,503 Farrington Jan. 18, 1943 2,319,630 Prutton May 18, 1943 2,322,093 Moran June 15, 1943 2,329,436 Cook Sept. 14, 1943 2,349,785 Faust May 23, 1944 2,405,608 Rogers Aug. 13, 1946 

1. A LUBRICATING COMPOSITION COMPRISING MINERAL LUBRICATING OIL CONTAINING 0.1% TO 3.0% BY WEIGHT SUFFICIENT TO IMPART ANTICORROSION PROPERTIES TO SAID OIL OF A COMPOUND OF THE CLASS CONSISTING OF MERCAPTALS, MERCAPTOLS AND TRITHIO ORTHO ESTERS, SAIC COMPOUND CONTAINING AT LEAST ONE SUBSTITUENT -OR GROUP WHERE R REPRESENTS A RADICAL OF THE CLASS CONSISTING OF HYDROGEN AND HYDROCARBON RADICALS.
 2. A LUBRICATING COMPOSITION COMPRISING MINERAL LUBRICATING OIL CONTAINING 0.1% TO 3.0% BY WEIGHT SUFFICIENT TO IMPACT ANTICORROSION PROPERTIES TO SAID OIL OF AN OIL-SOLUBLE METAL SALT OF THE PRODUCT OBTAINED BY TREATING BETWEEN ABOUT 5 AND ABOUT 7 PARTS BY WEIGHT OF A COMPOUND OF THE CLASS CONSISTING OF MERCAPTALS, MERCAPTOLS AND TRITHIO ESTERS WITH ONE PART BY WEIGHT OF A PHOSPHORUS SULFIDE AT A TEMPERATURE BETWEEN, 122* F. AND 302* F.
 4. A LUBRICATING COMPOSITION ACCORDING TO CLAIM 2 IN WHICH SAID OIL-SOLUBLE METAL SALT IS A CALCIUM SALT. 